Segmentation Fault 11 on upgrading to Swift 2.0

I have an iOS project that as of yesterday was working perfectly. Now I've updated to Xcode 7, bringing Swift 2.0 syntax. I went through and resolved all the errors as suggested to use new syntax. When I try to build, the build fails with a "Command failed due to signal: Segmentation fault: 11". This occurs on 4 different files.

The problem is, those four files didn't have any code that needed updating, and are quite simple files (on of them doesn't do anything but set a label to a property value). What gives?